Machinability of additively manufactured titanium alloys: A comprehensive review

Titanium alloys (Ti) are widely used in a number of industry sectors due to their outstanding physical and mechanical properties. However, these properties result in high cutting forces and temperatures during the machining process, which deteriorates the machinability of titanium alloys. Recently, additive manufacturing (AM) technologies have been used to fabricate Ti parts with complex contours. These AMed parts, although being near-net shape, require finish machining operation due to poor surface integrity. This paper presents a comprehensive state-of-the-art review on the machinability of titanium alloys fabricated by various AM techniques, in the light of investigations carried out to understand the cutting forces, surface finish and tool wear when machining/micro-machining AMed Ti. Moreover, the influence of cooling/lubrication methods and material properties of the AMed parts was also analyzed. From this review, it was found that the improvement in the mechanical properties of the AMed Ti led to larger cutting forces and higher temperatures, which significantly affected the tool wear and surface quality after the finish machining post-processing operations. Nonetheless, there is very limited literature that reports on significantly improving the machinability of AMed Ti components, which requires significant research attention in future studies.